The present invention relates to a low phosphorus lubricant composition and method for lubricating an internal combustion engine, providing improved oxidation resistance, wear and friction reduction.
The impending low phosphorus and low sulfur restrictions proposed in GF-4 PC-10 engine oil specifications have caused the need to invent new engine oil additives to supplement and eventually replace zinc dialkyl dithiophosphates, ZDP. In engine oil formulations, ZDP is the largest contributor of phosphorus to the additive package, hence the industry must lower the amount of ZDP in additive packages to meet current and future engine oil requirements.
The present invention was developed to solve the problem of lowering the phosphorus levels in an internal combustion lubricant while maintaining or improving oxidation resistance, wear and friction reduction. The invention provides a zero phosphorus anti-wear additives with the potential to serve as friction modifiers and antioxidants in PCMO, HD, and other applications.
U.S. Pat. No. 4,952,328, Davis et al., Aug. 28, 1990, discloses lubricating oil compositions for internal combustion engines, comprising (A) oil of lubricating viscosity, (B) a carboxylic derivative produced by reacting a succinic acylating agent with certain amines, and (C) a basic alkali metal salt of sulfonic or carboxylic acid. An illustrative lubricant composition (Lubricant III) includes base oil including viscosity index modifier; a basic magnesium alkylated benzene sulfonate; an overbased sodium alkylbenzene sulfonate; a basic calcium alkylated benzene sulfonate; succinimide dispersant; and zinc salts of phosphorodithioic acids.
U.S. Pat. No. 4,981,602, Ripple et al., Jan. 1, 1991, discloses lubricating oil composition for internal combustion engines, comprising (a) an oil of lubricating viscosity, (b) at least one carboxylic derivative produced by reacting a succinic acylating agent with certain amines, and (c) at least one metal salt of a dihydrocarbyl dithiophosphoric acid produced by reacting phosphorus pentasulfide with an alcohol mixture, wherein the alcohol mixture comprises isopropyl alcohol and aliphatic alcohol and the metal is a Group II metal, aluminum, tin, iron, cobalt, lead, molybdenum, manganese, nickel or copper.